CONTROL DE LA DERIVA DE PISO

Theoretical Proposition: Forage crops hinder economic, environmental and social sustainability. Rival Explanation: Forage crops enhance economic, environmental and social sustainability.

Although farmers favour wintering on grass, forage crops allow them to winter more cows on a smaller area and helped manage the risk of being unable to grow and transfer enough feed to fully feed cows in winter.

The relative viability of crop or grass based systems depended on local conditions. On dryland Canterbury DSL for example, it does not seem to be viable to rely on grass for winter feed, while in parts of Northern Southland, the summer dry means that it can be very difficult to grow good crops and that grass may be a better option for winter feed:

‘Well basically in November it just blows like buggery up here eh. And that’s when you’re trying to do all your cultivation you see trying to get your Swedes in. You’re

losing all your topsoil at the same time.’ [3A]

Any wintering method can result in negative environmental impacts such as soil damage or runoff to waterways. Grazing management over winter and developments such as drainage were a more important determinant of impacts on the soils than the kind of forage involved. For example on pasture near a self-feed silage stack:

‘This paddock will have to be re-done. I just don’t know what we’ll do with it next, because we can’t do it here again, it’s too destructive, we might be able to do it for

another year’ (Plates 4 & 5: Self Fed Stack 1-2) [3B]

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The advantages of wintering on grass are improved control of feeding, the ability to avoid diet changes and possibly enhanced spring production. Secondary advantages include simpler management, cost savings and synergies with other enterprises such as youngstock grazing and silage making.

It appears that all grass DSL units require less input of resources and management time than systems that involve forage crops…

‘There are no crops. Because I’ve got other kinds of stock here, heifers and so on, the amount of time that the ground is out for. A mob of 200 heifers at 7 bucks a week and

then in 25 days I do it again, if put in a crop I can’t, its out for five months maybe

longer. I winter my cows on there for 30 days, well if you work out your sums, you’re

better off to run your grazers through it, plus its easier to manage and most of the pastures are all new and while I was toying with the idea of putting it into permanent

crop, it’s just as easy to put it into permanent pasture again.’ [1B]

…there may also be improved synergies with other enterprises:

‘I think that in the end it is better for me to do all grass because I have the area already for the beef… and uh I make silage again. I think it works, I do not have to shift them

twice a day, I don’t have hassles with the other feed.’ [2C]

Another advantage of using grass is that it appears to be easy to make objective measurements of how much cows are being fed:

‘…if you get a drought at the wrong time, you’ll only grow a 7 to 8 ton crop and

everyone will say; ‘there’s 10 tons in there’ well it’s not it’s a load of s***, they are

normally 2-4 ton lighter than what everyone reckons.’ [3A]

An all-grass diet avoids the need to do a feed transition, which is better for cow health: ‘No nitrate hassles or crop problems because I use grass.’ [1B]

There may also be ongoing benefits in terms of improved cow production in spring, however it is unclear whether the reported enhanced production is due to improved cow health or the high level of utilization and control of feeding that occurs with cows strip grazed on grass:

The first year we increased spring production by 24 per cent on the previous season, the second season I fine tuned it and we did it better and we did 24 per cent more again and

then last season we cocked it up and we run short of feast which was our late winter feed and I started getting skinny cows and we dropped by 30 per cent. That’s a real

major.’ [3A]

Grass systems are also more exposed to the inherent variability of dryland, with the potential for feed deficits and liabilities for the whole system:

‘Even though it’s very lightly stocked, it puts a lot of pressure on the whole system because all of a sudden you’ve stopped growing grass.’ [2B]

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Ideally all-grass systems are irrigated, thus mitigating the risk of relying on one type of forage for winter feed. Irrigation will also allow maximum control over pasture growth and pasture quality. Grass wintering is likely to involve other enterprises such as youngstock grazing or bull beef which need to be integrated with the overall system.

It appears to be important to offer high quality feed to the end of winter and it may be necessary to select grass species accordingly:

‘You’ve gotta have a real high energy feed going into them late in winter because the

calves so big and the stomach’s so small, they’ve gotta eat high energy so they don’t basically go skinny. And when they go skinny they go skinny from the inside out. You’ll

turn up one day and they’ll just be toastracks. And that just turns into hell. So that’s why I’ve sown all this out in Feast.’ [3A]

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Forage crops facilitate the transfer of large amounts of high quality feed to winter and give an improved risk profile relative to all grass systems. The main difficulties with crops are the costs involved and dietary issues that can occur with cows:

With forage crops, the system will have two sources of forage to provide winter feed, with two distinct critical times (establishment for forage crops and autumn for grass).

With the involvement of crops there will be more feed carried through to winter…

‘This is dryland kale and we’ve done quite a lot of dryland kale over here, we get at

least an eight ton crop each time, no matter how dry it gets’. [2B] …improved risk management…

‘…trouble is, we get an autumn that you can’t count on sometimes, if you knew you were going to be growing 50 (kg drymatter) a day through March-April, you could set it

up quite easily to winter on grass, but you can’t count on it and if you don’t get it you will be forced to be grazing some off.’ [3C]

…and an improved ability to manage grazing in winter:

‘Cropping proved to us that in the most adverse winter we could get through and up the ante.’[1A]

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For success with crops, measures must be taken to maximize crop yields and to minimize the impact of cows on the soil.

Timing of implementation and attention to detail appear to be crucial because of the sensitivity of crop yields to crop preparation tasks. Crop preparation tasks need to be carried out properly and at the right time to maximize yields and utilisation…

‘The swedes are all ridged… the drill moulds up the soil, the lighter sowing rate, it keeps them… it is condusive to growing bigger swedes which cows do utilise better than

a whole lot of wee dudes. They don’t waste as many by standing on them. With ridging

them you do get better utilisation, you are normally guaranteed at least an average

crop… it’s a more reliable way of growing swedes.’ [4C] …or to avoid losses:

‘Oh, I reckon probably 6-7 ton and it was shaping up to be 12 ton… because I know that paddock, we didn’t get it right, we were running late probably and put disks through it, and didn’t plough that one, that was the last paddock we ate off last winter

and the contractor had been, he had ploughed it all and then gone.’ [3D]

It appeared that with good practice, forage crops can be grazed in a range of situations while avoiding mud, soil runoff and damaged soil structure. Practices such as proper drainage, small mob sizes, back-fencing and using machinery appropriate for the situation all appeared to be effective in reducing the amount of mud:

‘This is where cows have been wintered, there’s been a lot of back fences put up there and that ground there is absolutely spot on. No problems whatsoever… you don’t see a

whole lot of tracks there from machinery, we use silage, not balage, but he uses fairly

big machinery to pull the silage around. You can see he’s got back fences up. (Plate 7:

Post Grazing).’ *Observed the post-grazed soil to have an appearance and texture as if it had been lightly cultivated rather than pugged. [4A]

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ƒ Wintering on grass is believed to be better for animal health, is easier to manage and fits

better with other enterprises such as grazing young stock and beef. But it only works financially if production from grass approaches that of an equivalent area of forage crops in the same conditions.

ƒ Forage crops help manage risk. Exceptions to this were a DSL unit in an area where early

summer conditions make crop establishment difficult (Case 3A) and 100 per cent irrigated DSL where there is complete control over pasture growth (Cases 1A and 2C).

ƒ Undesirable environmental impacts or production losses can occur under any wintering